I could do without having to build all 30 SCVs/probes/drones at the start of the game.

Scouting innovations would be nice too - what wrecked a lot of WC3/Starcraft was the use of map revealer mods that gave the cheating player a massive strategic advantage. Hell, just playing the whole game without any fog of war at all would be a bold, interesting move. I got addicted to Terran because I could beat people I knew just by Comsat stationing their early stuff and building accordingly. (Which, oddly, usually resulted in massed Firebats with Medics. Walking all over someone's zealots is a lot of fun.)

Rush tactics are annoying as hell, right up until the point you become a good players and then they're hilarious. Some troubles there (early defense as terran was a bitch), but also not something you want to remove.

Also setting the game to ONE speed only, ever, would probably help balance. I don't know about what Fist said, WC3 was micro heavy, Starcraft on fastest speed was just a matter of building a few bases and swarming the map with 130 Hydralisks and 10 Guardians. Some units had amazing powers, but they required you to be there to use them, and that was a fatal distraction from resource/base control. At the higher speeds there were literally only about 2-3 people in the whole who could play Terran competitively for a long while. A "realistic" fastest speed for people without 1000 hours drill playing on a half seconds internet lag would be a strong move.